The present invention relates to an electrochemical cell such as a fuel cell and an electrolytic cell employing a solid polymer electrolyte (hereinafter referred to as "PE") and having a structure of wetting the solid polymer electrolyte for attaining high performance.
A fuel cell has been developed as an anti-pollution electric power generator having high energy efficiency in view of problems of exhaustion of energy resources and global environmental pollution.
A fuel cell employing PE is expected to be a lightweight and high power generator which may be useful as a small-size electric source for an electric automobile or the like (disclosed in reference 1; D. Watkins et al., Proceeding of the 33rd International Power Sources Symposium, PP.782 to 791, 13 to 16, June (1988), and in reference 2; E. A. Ticianelli et al., J. Electrochemical Society, 135, 2209, (1988)).
An electrolytic cell using PE is expected to be employed in electro-synthesis starting from such a gaseous hydrocarbon or alcohol as methanol and the like in future.
The performance of these cells is largely influenced by the ionic conductivity of PE employed.
When a sufficient amount of water is not contained in PE, its conductivity considerably decreases with the increase of its resistance to lower the cell performance.
In order to overcome the said drawback, a reaction gas (a hydrogen gas as fuel and oxygen or air as oxidant) containing water vapor may be introduced into a cell.
Since, in this improved cell, a partial pressure of the reaction gas decreases due to dilution with the water vapor by the partial pressure of the water vapor, and further diffusion of the reaction gas in the reaction layer of an electrode is depressed, the characteristics of the cell may be deteriorated.
Since the water pressure which changes with a changing load cannot be sufficiently controlled, PE is dried or the catalyst layer is inversely overwetted resulting in the deterioration of the cell performances.
A larger amount of H.sub.2 O is exhausted in an anode side because several molecules of H.sub.2 O are accompanied with an H.sup.+ ion permeating through PE from the anode to the cathode of which an amount is proportional to a current. However, it is difficult to overcome by the said water vapor mixing process (disclosed in reference 3; T. Springer et al., Extended Abstract No.118, J. Electrochemical Society Meeting, vol.190-2, October (1990)).
Accordingly, these problems should be inevitably overcome for employing the fuel cell as a moving electric source of which a load largely changes, and the same problems exist for an electrolytic cell using PE.